Remove scikit-image runtime dependency

ccdproc's block_reduce/block_average/block_replicate wrappers
delegate to astropy.nddata -- skimage was never called at runtime.
The version-skip decorators in the test file used broken string
comparison and guarded against an old numpy dev incompatibility
that's astropy's problem now.

Closes #921.

Author: karlhillx

CHANGES.rst

@@ -5,6 +5,7 @@ Other Changes and Additions
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 - Remove superfluous license file from the package. [#899]
+- scikit-image is no longer a runtime dependency. [#921]
 
 2.5.0 (2025-07-03)
 ------------------

ccdproc/tests/test_ccdproc.py

@@ -7,7 +7,6 @@
 import astropy
 import astropy.units as u
 import pytest
-import skimage
 from astropy.io import fits
 from astropy.modeling import models
 from astropy.nddata import (
@@ -801,10 +800,6 @@ def tran(arr):
 
 # Test block_reduce and block_replicate wrapper
 @pytest.mark.skipif(not HAS_BLOCK_X_FUNCS, reason="needs astropy >= 1.1.x")
-@pytest.mark.skipif(
-    (skimage.__version__ < "0.14.2") and ("dev" in xp.__version__),
-    reason="Incompatibility between scikit-image " "and numpy 1.16",
-)
 def test_block_reduce():
     ccd = CCDData(
         xp.ones((4, 4)),
@@ -834,10 +829,6 @@ def test_block_reduce():
 
 
 @pytest.mark.skipif(not HAS_BLOCK_X_FUNCS, reason="needs astropy >= 1.1.x")
-@pytest.mark.skipif(
-    (skimage.__version__ < "0.14.2") and ("dev" in xp.__version__),
-    reason="Incompatibility between scikit-image " "and numpy 1.16",
-)
 def test_block_average():
     data = xp.asarray(
         [

pyproject.toml

@@ -21,7 +21,6 @@ dependencies = [
     "astroscrappy>=1.1.0",
     "numpy>=1.26",
     "reproject>=0.9.1",
-    "scikit-image",
     "scipy",
 ]